x86: Support for GRUB in the Oracle Solaris OS

The following sections contain additional reference information for administering GRUB in the Oracle Solaris OS.

x86: GRUB Terminology

To thoroughly grasp GRUB concepts, an understanding of the following terms is essential.

boot archive

A collection of critical files that is used to boot the Oracle Solaris OS. These files are needed during system startup before the root file system is mounted. Multiple boot archives are maintained on a system:

• A primary boot archive is used to boot the Oracle Solaris OS on an x86 based system.

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  Note - On the x86 platform, when you install the Oracle Solaris, two primary boot archives are created, one 32-bit archive and one 64-bit archive.

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boot loader

The first software program that runs after you power on a system. This program begins the booting process.

GRUB

GNU GRand Unified Bootloader (GRUB) is an open-source boot loader with a menu interface. The menu displays a list of the operating systems that are installed on a system. GRUB enables you to easily boot these various operating systems, such as the Oracle Solaris OS, Linux, or Windows.

GRUB main menu

A boot menu that lists the operating systems that are installed on a system. From this menu, you can easily boot an operating system without modifying the BIOS or fdisk partition settings.

GRUB edit menu

A submenu of the GRUB main menu. GRUB commands are displayed on this submenu. These commands can be edited to change boot behavior.

menu.lst file

A configuration file that lists all the operating systems that are installed on a system. The contents of this file dictate the list of operating systems that is displayed in the GRUB menu. From the GRUB menu, you can easily boot an operating system without modifying the BIOS or fdisk partition settings.

primary boot archive

See boot archive.

x86: Functional Components of GRUB

GRUB consists of the following functional components:

• stage1 – Is an image that is installed on the first sector of the fdisk partition. You can optionally install stage1 on the master boot sector by specifying the -m option with the installgrub command. See the installgrub(1M) man page and Disk Management in the GRUB Boot Environment in System Administration Guide: Devices and File Systems for more information.

• stage2 – Is an image that is installed in a reserved area in the fdisk partition. The stage2 image is the core image of GRUB.

• menu.lst file – Is typically located in the /pool-name/boot/grub directory on systems with a ZFS root. This file is read by the GRUB stage2 file. For more information, see the section, x86: Modifying Boot Behavior by Editing the menu.lst File.

You cannot use the dd command to write stage1 and stage2 images to disk. The stage1 image must be able to receive information about the location of the stage2 image that is on the disk. Use the installgrub command, which is the supported method for installing GRUB boot blocks.

Naming Conventions That Are Used for Configuring GRUB

GRUB uses device-naming conventions that are slightly different from previous releases. Understanding the GRUB device-naming conventions can assist you in correctly specifying drive and partition information when you configure GRUB on your system.

The following table describes the GRUB device-naming conventions for this Oracle Solaris release.

Table 10-1 Conventions for GRUB Devices

For more information about fdisk partitions, see Guidelines for Creating an fdisk Partition in System Administration Guide: Devices and File Systems.

Naming Conventions That Are Used by the findroot Command

Starting with the Solaris 10 10/08 release, the findroot command replaces the root command that was previously used by GRUB. The findroot command provides enhanced capabilities for discovering a targeted disk, regardless of the boot device. The findroot command also supports booting from a ZFS root file system.

The following is a description of the device naming convention that is used by the findroot command for various GRUB implementations:

• Standard system upgrades and new installations for systems with ZFS support:

  findroot(pool_p,0,a)

  The p variable is the name of the root pool.